Fluid pressure actuated reversing valve for hydraulic rams



Oct. 21, 1952 W/ERNST 2,514,539

FLUID PRESSURE ACTUATED REVERSING VALVE FOR HYDRAULIC RAMS Filed Dec. 7, 1946 6 Sheets-Sheet 1 INVENTOR WALTER E RN ST ATTORN EYS Oct. 21, 1952 w. ERNST 2,614,539

FLUID PRESSURE ACTUATED REVERSING VALVE FOR HYDRAULIC RAMS Filed Dec. 7, 1946 6 Sheets-Sheet 2 INVENTOR WA LT E R E R NST BY 'Joul/mjm Um ATTORNEYS 6 Sheets-Sheet 5 KIN R ERNST WAL ATTORNEYS m lfifiav viii\\\\\\\\\\\\\\\\\\SS\\\ W. ERNST S\\\\\\\\\\\\\ II WEE? FLUID PRESSURE ACTUATED REVERSING VALVE FOR HYDRAULIC RAMS Oct. 21, 1952 Filed Dec. 7, 1946 W. ERNST Oct. 21, 1952 FLUID PRESSURE ACTUATED REVERSING VALVE FOR HYDRAULIC RAMS 6 Sheets-Sheet 4 ll M Filed Dec. 7, 1946 INVENTOR WALT E R E R N 51 f jaujmu'm Jul/min ATTORNEYS Get. 21, 1952 w. ERNST 2,614,539

FLUID PRESSURE ACTUATED REVERSING VALVE FOR HYDRAULIC'RAMS Filed .Dec. 7,1946 6 Sheets-Sheet 5 Z /l/l/l/l/ INVENTOR L j WALTER ERNST ATTORNEYfi FLUID PRESSURE ACTUATED REVERSING VALVE FOR HYDRAULIC RAMS Filed Dec. 7, 1946 6 Sheets-Sheet 6 r )11 '20 '5 I64 I us m um U-u2 I62 T 238 lNVENTOR WALTER ERNST BY r JouB/mim ATTORN EYS thegreatest thrust 'With drawing and forming operations, the load may extend f it-will be seen tremely high speeds press in which VALVE FOR H-YD RAULIQLRAMS Walter. Mount. Gilead, onit, assign'or to H-P-M Development Corporati'omwilmington, Del.,' a corporationof Delaware I Application December 7,1946, s rri'Nt. 714,840

Q 4 c aim (01; rat-46.5)

'I his invention rel'atesto achine tools as particularly to presses. p t

The particular object of the Present invention is to provide an improved type hydraulic press having the-desirable characteristics of both Ii'le chanical and hydraulic presses. 1 I I In the class of work for which presses are employed, there are a variety of work cycles such as forming, blanking, piercing and drawing which work cycles vary in their requirements. For eX- ample, blanking and piercing operations are generallycarried out at highspeed-and the exact strokeof the working member of the press is not critical so long as it carries the punch completely throu h theworkpiece being blankedor pierced. On the other hand, forming and drawingoperations, are usually not carried out at high speeds and the stroke of the plunger is critical because the drawing member or punch generally bottoms against the stationary die or against the work piece being drawn. v

Also, in blanking and piercing op.erations the 'load onthe punch is momentary,1being in the nature of shock load, and is concentratedat the point of travel of the punch where it is receiving from its actuating member.

is more uniformly distributed and over a large part of the punch travel. From this,

that a press to be universally useful must be able to operate at. high .sp'eed, to possess sufficient reservepower tov withstand the impacts on the punch during blankingand pierc in'goperations, and stroke adjustment of the member. carrying the punch, and have the characteristic of developing a highforce on the said member during a large part of the travel thereof. H t

One of the objects of the present invention is 1 to provide a press of this type,

. Still another object is to provide ail-hydraulic press having an operating circuit byf neans of' which the press ram can be reciprocated at ex:

. Still another object is to :provide a hydraulic press having a recipro'cable ram-and a control circuit therefor by means of which the ram can be cycled at high speed 'm'atic. cycles as desired. j v v I I I It is a still further object to provide a hydraulic is readily adjustable for acconunodatingdiffer'ent die sizes;

A still further object is toprovideanioiw fa i e through single or auto;

2. motor such-that the'pump is carried power-loads 1 without losing any amount offspeed.

These and other objects and advantages will become more apparent upon reference to thefollowing description taken in connection with the attached drawings in which:

Figure 1 is a front elevation of a press constructed accordi to this invention;

Figure'2 is a side View of a press constructed according to this invention and partly broken away to'show the construction thereof;

Figure Bis a plan section indicated by the line 3"--3 on Figure '1 Figurefllv is a vertical section indicated ,by the line 4-9-4on Figure 3 andshowing anadjustable over peaka cam for actuating one of the control valves;

for the ram and is indicated by the line 6-6 on Fi urefi; v I

Figure '7 is a diagrammatic showing of the operatingcircuit for the press ram; Figure 8 is a sectional view through the main operating valve of thecircuit of Figure 7;

be arranged for speed and I the position of the movable platen Figure 9 is a diagrammatic showing of the control circuit for the ,valve of Figure .8; jFigureslOand '11 are views of the selector valves of the control circuit of Figure 6 in position for manual cycling of the press ram; and Figures 12 through 14 are energy charts showing the effect of the pump motor and'flywheel arrangement, of this invention.

Structural arrangement Referring tothe drawings, Figures 1, 2 and 3' illustrate a press having a frame 10 which may be of plate suitably braced by cross-structural member's but which, preferably, is cast in one piece. The I'rame l0 ispivoted as at l2 to a pair of basemembers l4, and is angularly adjustable in'the said members about the pivots l2 by a piston and cylinderarrang'ement indicated at l6fwhichis pivoted'to thesaid frame atl8, and to thfejbas'ejmembers at 2 0.. Actuatingfluidi is directed to on'efend or the other of the piston and cylinderarrangement by a distributing valve 22 whichis'locatedto be easily available to the press operator. The press frame may be retained in 7 any of severalangularpositions bythe pins 24 which pass through an aperture in the press frame andinto one of several apertures 26in the base members 14.

substantial ply of fluid from-the pump 34 .to the cylinder 30.-

The pump 34 is preferably of the adjustable stroke type in order to provide for a variable delivery to control the speed of operation of the press ram, and is carried on a base 36 ;which is mounted on a bracket 38 the press frame.

the pump and motor is a flywheel 42. The motor 40 is preferably of the high slip type so that dur-'- ing the time that the pump 34is under load, the pump motor and flywheel will slowdown and carried onthe back of The pump 34 is driven'by a motor 40 and carried on the drive-shaft between relieve excessive pressure from T if necessary.

energy will be extracted from the flywheel and,

thereafter, when the load is removed from the pump and the pump, flywheel and motor begin tdl'speed up energy will be supplied to the flywheel. V

The construction of the press ram and! platen isbes't' 'seen'in Figure wherein it will be seen that the press ram '44 extends into the cylinder 30 through the packing 46 and has connected thereto at the upper end the separable head portion'48 as by the bolt 50, The head portion 48 includes the piston rings '60 which prevent leakage'of fluid around the said head.

The head or piston 48 is provided with a pair of bores 62 into which 'extend'the booster rams which are rigidly carried in the cylinder head 66., The cylinder head 66 is bolted to the end of the cylinder by a plurality of bolts 68 and the resilient 'sealingring prevents leakage of fluid around the cylinder "head. The head 66 also has "a central port 72 therein which communicates, as s'een in Figure'6, through the openings 14 with i2 includes a valve "seat against which seats the poppet 'tvpe surge valve member 76 whichh'as a spring 18 serving continuously to urge the said valve-"member against its seat, and a piston "80 which is supplied with "pressure fluid through a conduit-J2 for moving the surge valve member into its open position, I v

The ram-'44"extends downwardly from cylinder and has a threaded end portion as area thereon whichfisengaged by'anut 86. The nut 86 is carried-in 'a recess in the "upper surface. oi the press platen 88'andi's movablein angularrnovements as by a spanner wrench adapted for en gagement'with the recesses 90. The nut 86 is adapted for being locked'in any position of adjust ment by the clamping ring :92 which is secured to the platen 88 by the screws 94 which can be loosened to permit rotation of the nut 86 and tightened to clamp the nut in place. f I The platen 88 has laterally extending portions thereonas at '96 which are receivable in "'guideg way's 98 in the press frame, so thatthe'platen is guided torecipro'cate in a straight line toward and awayyfrom the press bed.

The Y platen may have the cross passage I 00 therein through which extends the knockout bar I02"which,'in'-turn, carries theknockout pins I04 which-extendintoa'punch "or die carried by the platen. Carried on the pr'essframe infthefbrac'kthe 'ch'amber'28; The port ets-I06 arethe adjustable screws I08 which,

when the platen is fully "retracted, engage the knockout bar '-I 0' 2 -a'nd therethrough "actuate the knockout pins I04 -to "dislodge "workpieces from the punch ordie carried on the platen 88.

4 Operating circuit The operating circuit for the press ram is best seen in Figure 7 and the valves therefor will be seen in section in Figures 5 and 8. In Fig ure 7, it will be seen that the pump 34 draws fluid from the chamber or reservoir 28 through. a conduit H0 and expels the said fluid through a conduit II2 into the inlet of the main operating valve II4. The conduit II2 may also open through a relief valve II 6 to the reservoir to the said conduit The valve H4 is connected by a conduit H8 7 with the booster rams 64, and by a conduit I20 with the retracting side of the ram 44. The conduit 82 leading to the surge valve in the top of the press cylinder is also connected with the conduit I20.

The conduit I20, adjacent the cylinder 30 includes a resistance valve I22 which is best seen in Figure 5. This valve includes a checkvalve I24 opening toward the cylinder 30, and a spring loaded valve member I26 which passes fluid away from the said cylinder. It will be noted that the valve member I26 includes a downward acting area which opposes the thrust of the spring I28 and, at a predetermined pressure permits fluid to be expelled from the retracting means of the ram. This prevents the ram and platen from dropping under their own weight when the press sets idle.

The valve H4 is best seen in Figure 8 wherein it will be noted. that the valve comprises the casing I30 having a valve bore I32 which is intersected by the inlet port I34 which is connected with the pressure conduit II2, the service ports I36 and I38 which are connected, respectively, with the conduits I20 and I I8, and the exhaust ports I40. The exhaust ports are connected, as seen in Figure "7, with the reservoir 28 by means of the conduit I42.

Reciprocable within the valvebore- I32 is a valve member having the spaced spool portions I44 thereon. The spool portions are notched as at I46 so that when the valve member is in its center position as shown in Figure 8, there is a restricted passage connecting the inlet port I34 and the service ports I36 and I38 with exhaust. The valve member comprises stem portions extending each way therefrom through axial bores formed "in a pair-of annular plugs closing the opposite end-s of the valve'bore I32, and have shou'lders thereon as at 148 which engage pistons I50 that reciprocate in the cylinders I52. The pistons are also backed up by the springs I 54 which operate to urge'the pistons I50 against the plugs, and thereby serve as centerin springs for the valve member.

The stems of the valve member also extend into the end cylinders I56 and'are abutted therepressed air. The piston on the left end oi'the valve as seen-in Figure'8 receives compressed air from the conduit I60 while the lpiStOI'l on the right end of the valve receives compressed air from the conduit I 62. I 7

Each of the'cylinders I52 is hydraulically "connected .with th service port on the oppositeyend of the valve. These connections are indicated by the conduits at I64 and ar operable to prevent the shifting of the valve memberbeyond'its center position to connect either of the service ports with exhaust whenever there .is more than a predetermined pressure standingin'the said pressed pressed air from the source 200 andfthe valve members 220.

' port. This prevents the: sudden I release of fluid from either .isidexorrthe press ram while -;under pressure :and thereby-i preventsi shock and vibra tion of the press .at the timeof reversaL. r For example, when the valve member is shifted rightwardly; asaviewed fromiFig. 8, bylntroduc-. ingfiuid pressureinto the left-hand cylinder I56, fluidv from-conduit. I I2 passes into conduit I I8,- whileconduiti'.I201 is connected with the lefthand exhaust port I40 This causes the ram 44- to advance until-resistance is encountered. At this time, compressed air may be ;introduced by way of the conduit I62 ,intothe right-hand cylin der I56 to shift the valve member leftwardly.

' Howevenga-sthe,valvegmember reaches its centered position, the left-hand shoulder portion I48 engages} he pistonflm, and if the fluid pressure within the left-hand cylinder I52 is sumciently greater than the pressure of the comair acting on; the right-hand piston I58, due to the build-up of pressure within the con-l duitsIlB and I64, the valve member will remain in itscentered position until the build-up in pressure, is relieved within the left hand chamber I52, the conduit I64, and'thecon'duit IIB byway of thef'notches' I46 in the right-hand spool mem.

bef I454. Thereaften'the pres-sure of the com pressed air introduced byway or the conduit I62 will shift the valve member leftwardly to'connect the inlet port I34 with theleft-hand service port I 36; while fully connecting the conduit I I 8' with exhaust.- Thus, the'pressures within'the respective pressureareaso'f theramf are relieved gradually upon'shiiting of compressed air pressure upon the opposite pistons I58. Z

--Control circuit Figure 9fillustrates'" control circuit for contr 'b uhg the actuationof the reversing valVe.I-I4.

In Figure 9, there isa source of fluid such as coin; pressed airindicated'at'200. The supply of comv p to thevalve is controlled by-th'epositions' occupied by the shift 'valves indicated at 202, 204and 20G. The valve v 202 comprises a-pair ofipiston portions 208 and 2H) which aremovable alternately into open andclosed positionbya lever 2 I 2 which is actuated by the do'ubleactingplunger 2I4. The smaller area ofithe plunger 2I4 is continuouslyfsupplied with pressure fluid by aconduit 216 leadingv to the source200, whilepressureissupplied to the other side of y the piston through various selector valves to' be described hereinafter. s I. "[Thev'alve 204 has the valve members 2I8, 220, 206 has the valve me berszzz and 224, the said valve members being alternately movable into n open and closed" position by the levers 226 and 228-.which are connected for simultaneous actuaton by the double acting piston 230.

- The upper, smaller area of'the piston 230 is contlllilOlISlY'SllPPliGd "with pressure from the source a conduit 232' while the lower, larger. surface thereof is selectively supplied withipressure fluid by'the aforementioned control valves;

The valves 202, 204 and 206 are connected thevalve I'I4 through a pair of selector valves 234 and 236' which select between automatic and manual operation according to their position.

The valve 234 includes-a movable portion indicated at 238 which is movable from the position shown in Figure 9 into position shown "in Figures 10- and 11. Inthe position shown in Figure-9; the valve 234 connects'the conduit I60with the '*conduit240which leads to one side of the'valve ..;The;iva1Ve:.234: also connects the conduit I62 with the conduit 24:. which leads to one side of: the. valvemember 208.1: Thevvalvc 234'also connects the conduits244-and'246 which lead to the valve. 236 :and within which the said conduits are interconnected. I

'- The conduit .242 which leads of thevalve member -2I0 the other side of which is connectedvto afconduit 248 with oneside of the valve member. 222L'uThere is also-a connece tion from the sameside ofthevalvemember 222 to one side of the valve member-22 I, the other side .of which is, connected directly with the exhaust. .The opposite side of the valve member 222is-connected with the pressure source 200 by a conduit250 so that with the valve in the ositionshown pressure is supplied to the conduit 2484 while if the valve is shifted the conduit 248 is connected with theexhaust -l Returning tothcfvalve 202, the side of the valve member opposite the conduit 242 is connected with the exhaustas at 252 so that in the position shown the valve member 202 connects the-conduits 242 withlexhaust while if shifted will connect the conduit 242 with the conduit 248. The valve member 204 in the position shown connects the, conduit 240' through the conduit 254 with exhaust at 256 and, when'shifted connects the said conduit 240 with the pressure source by the'conduit258.

For supplying pressure to the pistons 2 I4 and .230 there are'provided the pilot valves at 260,

262, 264 and 266. ach of the aforementioned valves is normallyclo sedand isadapted for being. opened at a predetermined time, or in response to a predetermined stimulus for either supplying compressed'air to, or exhausting air' from oneor both of the pistons 2I4, 230.

' The 'valve'266 is adapted for actuationbyj a foot'lever 261' andfwhen opened, connects the pressure conduit 2fi 8 vvith a conduit 210 leading to the valve 262." The valvej 2621s adapted for beingf opened by the lever 212; when the'ipress platen is in its"fully retr acted position so' that the pressure fluid fror'nthe"conduit210 jalsoj passes to the'conduit' 2'l4 andfromfthere is con;

ducted to the'lower sides of the pistons 230jand' 2I4. With the pistons in the positions 'shown,-"

the piston 230 is actuated upwardly to-open, the valve member 220 and 224 and toiclose the valve members 2I8 and 222 while the piston 2I4'remains in its upper position to'holdthie valve ZIiB;

open and to close the valve, member M0. j .j

With the valves so shiftedthe conduitIIiZ is exhausted through the {valve 234, the conduit 242 and the exhaust connection 252 while the conduit I60 is supplied with'pressu're' through the conduit'248 "and the conduit: 25t;--

"Thisshifts'the valve! I4 t0 place'the press on forward: stroke and to bring the ram do -vnwardly. When the ram has built u a predetei mined pressure, the plunger 276; is actuated thereby and'i'noves the alve 260 into position to exhaust the "lower area of the 'piston2I4 through the conduit 218 and 280, and the lower area ofthe piston 230 through the conduit 214,- check valve 282, and conduit 280. I This permits both of the pistons 2I4, 230 to move downwardly thereby to close the valve members 208, 220 and" 224 and to'ope'n the valve members 2 I0, 2 I8 and 222.?This brings about the exhausting of the-conduit I60 through the con duit 240,'the conduit 254' and the exhaust connection 256 andsupplies pressure fluid'through the conduit I62 to the conduits 242, 248 and 250. The press-then goes -on reverse "stroke as soon a's to one side of valve member 208 is also connected to one side the. valve. [114' shifts and the press ram come. mences its retraction stroke. As. the press ram approaches the upper'limit of its'travel, it actue ates the valve 264 into open positionbyrthe lever 284 and thus permitspressure fluid from the conduit 286 to pass through the conduit. 218 to the piston 214 to'move it into the position shown in Figure 9. V r i Asv best seen in Figure 4,. the valves 262 and 264 are adapted for actuation bythe cam means 263 adjustablycarried on the threaded spindle 265: of the platen 88.

As mentioned beforethe opening of the valve 264iexhausts both of the conduits. IE0 and IE2 andpermits the centering springs of the valve member Ill to move the valve member thereof to its center position thereby to bring the press ram to aha-1t.

Manual operation ofthe press may be had byopening the valve 288 which bypasses the valve 262. With'the valve 288 opened, the downward movement of the press is; controlled by holding the foot lever 26!- depressedand as soon as thelever 268 is released the press platen will return to its upper position. Full automatic cycling may be had by closing the valve 288 and opening the valve 290 which bypasses the foot operated valve 266'.

For hand operation of the press ram through out the cycle, the valve 234 is shifted into its Figure 10 position. wherein it connects the conduit I60 withv the conduit 244, the conduit I62 with the conduit 246. and connects the conduits 2'40, and 242 together. Thereafter, a. forward stroke of the press ram may be had by shifting the valve236 to connect the conduit 2'4'4'Wlt1lth6 pressure conduit 2 32 and the conduit 246 with the exhaust connection at 292. This supplies pressure to the conduit Hill. and exhausts theconduit I62. r

A reverse, stroke of' the press mayv be had by shifting the valve 236. to connect the conduit 244to the exhaust connection 292 while connecting the conduit 246 with thepressureconduit 232. It. will be apparent that full. manual operation obtains with the valve 234. in its Figures 1.0 and. 1.1. position.

Mot'onpump and flywheelcombination,

The combination of, the motor 40, flywheel. 42 and pump 34 operates on an energy transfer cycle. which is diagrammatically illustrated in Figures, 12 through 14. In Figure 12, there is. charted the energy which is received by. the pump., This is divided into a portion indicated at300. which is a continuous power consumption due to. friction, windage and, other fixed rotational losses-in. the pump. Periodically, audit is assumed. that the press ram is cycling automatically; at a. pref determined rate, there are; power requirements. represented by the peaks. at 302.

In Figure 13, there. is. illustrated the energy cycle of the flywheel 42, In comparing Figures; 12, and 13, it will benoted that the pump operates between upper andlower-limitsof power consumption and that, accordingly, by; using. a high slipmotor the. pump will decelerate. when it; is at the peak; power requirement, and accelerate; when the power requirements thereof are; at a m mum A qndins min F ure 13, t e-ener y. cycle ofthefiywheelis shown aeoscillating above and; below a median line 30! with; the areas be-. low the line, indicated at? 3106 representing energy; received; by: the flywheel: from the. motor.- during; he. periods of; accelerationuofa the; pumpzand; me-

ton" The'areas above the line 80.4, indicated at. 3 08; occur during the periods. of. deceleration. of, the pump and motor and represent energy given.- up by the flywheel andv transmitted to the pump.

Referring now to Figure 14, in conjunction with Figures 12 and 13, it will be found that the sum of the power requirements of the. pump andflywheel isi'a substantial-lyfiat line indicated at 3 I'll and being made up of the area 300 from Figure 12', the area 306. from Figure 13; and the areas 312 from Figure 12 which represent the difference between the peak pump requirements and the energy transferred to the pump from the flywheel. Y

It will be noted that the power requirements of the driving motor are substantially less due to the influenceof the flywheel than would be necessary if the pump were connected directly with the motor. Thus, a substantial saving in initial cost andoperating expense is obtained by the use of, the motor and flywheel combination of the present invention.

It will be understood that thisinvention is susceptible to modification in order to adopt it to different usages and conditions and, accordingly,

it is desired to comprehend suchv modifications.

withinthis invention as may fall within the scope of the] appended claims.

I claim:

1. In. a reversing valvefor hydraulic rams; an elongated, valve casing formedwith an axialvalve bore, a pressure inlet, a pair of service ports. andexhaust ports, all. of said ports; intersecting the valve bore at relatively spaced intervals there.- alon a spool type valvemember movable longitudinally within the. valve bore and having a pair of relatively spaced spool portionsfarranged for wiping engagement with the walls of the casing defining the valve'bore, andformed at their peripheral edges with a plurality of recessed grooves; said valve member being movable within the valve bore to a first centered" position establishing restricted communication between the inlet port'and' the'service and exhaust ports, and opposite and positions providing alternate. communication between the inlet port' and" each. of the service ports while connecting the opposite service port with exhaust, said valve member, bemg provided ateither end with. longitudinally extended stem portions projecting outwardly from either en-d'of the valve chamber and having shoulders thereon;- cylinder means carried. at either, end of said valve casing and enclosing the stemportions of'said valvemember; a first piston means in gsaid cylinder means} engageable. with the shoulders of" said valve member and normally urging said" valve member to its centered posia tion, said piston means being in. fluid. communi cation, with the service ports off said. valve, casing. andbeing operable", in response. to predetermined. high pressures at' said service: ports, to prevent movementof said. valve member, from.an endpor siti'on pastits. centered position. and toward. its opposite end position untilsaid predetermined high. pressures are. relieved; andv pneumatically operated' means. in, said cylinder means engageable. with the; stem portions-of said valve mem her for shifting;the-latter. between its end posi': tions.

2. In, a; reversing. valve. for: hydraulic rams; a". valve casing formed with. a valve bore, a. pressure inlet port; exhaust. ports: spaced from the pressure; inlet port, and

a. pair: or service ports I mtersectmg, the.-.valve.bore.b.etween the inlet-and exhaust ports; a valve position until said valve member until said predetermined high 9 r r v v member movable within the valve bore and formed with a pair of relatively spaced spool parts having notched edge portions disposed in wiping engagement with the the valve bore, said valve member being movable within the valve. 4 bore to a first centered position establishing rewalls of said casing, defining stricted communication, by way of the notched edge portions of said spool portions, between the inlet port and the service and exhaust ports, and opposite end positions establishing communication between either one of the service ports and the inlet port while connecting the opposite serv-' ice port with exhaust, said valve member being provided with relatively reduced diameter stem extensions projecting outwardly through the ends of the valve bore and formed with opposed shoulders; cylinder means enclosing the stem portions of said valve member; fluid-actuated stop means in saidcylinder means engageable with the shoulders'of the stem portions of said valve member and responsive to a given ,fiuid pressure at the service ports of said valve casing for arresting movement of said valve member from one end position to another in it's centered given pressure is relieved;

4. In a reversing valve for haust port, said ports intersecting the valve bore at relatively spaced intervals therealong; a valve member formed with spaced shoulders thereon and including relatively spaced spool portions said' casing, the

dis-

movable within the valve bore of spool portions of said valve'member being posed in wiping engagement with the Walls of said V valve bore and beingformed stricted communication between the inlet, service.

and exhaust ports of said casing, a first endposition connecting the inlet port with the first'service port and the second service port with exhaust.

and a second end position connectin the inlet port with the second service port and the first service port with exhaust; meansfor shifting said valve member between said first and second end spring means engaging said stop means for urging said valve member to its centered position;

and fluid-pressure-responsive means in said casing for moving said valve member between its end positions v v I 3. In a reversing valve for reciprocating hydraulic rams; a valve casing formed with a valve 1 chamber, an inlet port, a pair of service ports, and exhaust ports, all of said ports intersecting said valve chamber atudifierent levels therein; a valve member movable in and formed with relatively spaced shoulders, and having spaced spool portions engagement with the walls of said casing defining the-valve chamber, the spam portions of said grooves in the peripheral her to a first-centered position providing restrict being formed witha plurality of surfaces thereof, said' valve member-being movable in the valve chem-- the valve chamber thereon in wiping ed communication by way of the grooves in the v spoo1 portions of the valve member between the inlet, service, and exhaust ports, andopposite end positions establishing communication between the inlet port and either ofv the service ports while connecting the other service port with A exhaust; spring means in said casing arranged to urge said valve member to its first centered;

position; fluid-pressure-responsive means in. said a casing engageable with said valve member at op:-

. posite ends thereof for shifting said valve memberbetween its opposite end positions; and a, I pair of opposed fiuid-pressure-responsive plung- -ers slidable in said valve casing and'communicating, respectively, with opposite service ports of said casing and engageable with the'shoulders of said valve member when the latter moves from its centered position toward either of its oppm site end "positions, said plungersbeing responsive to a predetermined high pressure in the service ports of said'valve casing to delay movement of said valve member from one end position past its centered position to its opposite. end position 7 pressure in the service ports is relieved-by way of grooves in the spool portions of said valve member.

Number Name Date 1,943,061 Douglas Jan." 9; 1934 2,113,161 Osborne A9125, 1938 2,213,450 Munschauer s; Sept. 3, 1940 2,246,379 Muir et a1. "June 1-7, 1941 2,250,389 Miller July 22,1941 2,296,051 Pocock Sept. 15,- 1942 2,316,944 Ernst Apr. 20, 1943 2,324,697 Harrington July 20,1943 I 2,350,983 Boyles June 13, 1944, 2,351,317 Camerota June 13,1944 2,358,650 Maude Sept; 19, 1944 2,365,075 Hassman Dec.- 12, 1944 2,367,241 Stacy Jan. 16, 1-945 2,368,138 Hayden Jan 30, 1945 2,369,505 Ward Feb. 13. 1945 2,380,705 Proctor July 31,1945 2,390,849 Shoup Dec. 11, 1945 2,411,716 Ernst Nov. 26, 1946 2,429,669 Crawford Oct. 28, 1947 2,433,156 Pezzillo Dec."23, 1947 2,449,889 Eisen' Sept. 21, 1948 FOREIGN PATENTS Number Country Date 378,463 Italy Feb. 10, 1940 is relieved.

positions; a pair of opposed fluid pressure responsive plungers slidable in said casing and en- 'gageable with the shoulders of said valve member when the'latter moves from its centered position toward either of its first or second. end positions;

-- and means hydraulically connecting said plungcm, respectively, with the first and second service ports of said casing, said plungersbeing responpressure within the to arrest shitting position to its opposite end position in its centered position until said predetermined high pressure WALTER ERNST. REFERENCES orrnn The following references are of record in the 1 I file of this patentz a r UNITED STATES PATENTS H v hydraulic rams; a" 1 valve casing "formed with a valve bore, an inlet port, first and second service ports, and an ex- 

